Microtensile bond strength and failure modes of flowable composites on primary dentin with application of different adhesive strategies

Abstract

Background:Resin composite is an option for the restoration of primary teeth, and new materials with simplified procedures are increasingly being suggested.Aims:This study aims to evaluate the microtensile bond strengths and fracture modes of flowable composites on primary dentin with application of different adhesive strategies.Materials and Methods:Sixty extracted noncaries primary molars were abraded from buccal surfaces to expose dentin surface. The teeth were randomly divided into three groups as follows: Group 1, Vertise™ Flow (Kerr) (self-adhering flowable composite); Group 2, G-aenial Universal Flo® (GC Europe) (used with one-step self-etch system); Group 3, Tetric® N-Flow (Ivoclar/Vivadent) (used with two-step total etch system). Then, the flowable composites were applied to buccal dentin surfaces with the help of guide mold. Samples were embedded in acrylic blocks and sectioned to form dentin-composite sticks with a surface area of approximately 1 mm2. Finally, a total of 180 sticks were obtained to give each group of 60 sticks. Microtensile bond strengths were measured using a universal testing machine (1 mm/min). Fracture modes were evaluated with scanning electron microscopy.Statistical Analysis:Microtensile bond strengths data were analyzed by Kruskal–Wallis nonparametric test.Results:The microtensile bond strengths of G-aenial (15.5 megapascals [Mpa]) and Tetric (13.0 MPa) were statistically significant higher than Vertise (2.3 MPa). It was recorded that most of fractures in G-aenial was 40% cohesive, Tetric was 53.3% mixed, and Vertise was 83.3% adhesive.Conclusions:The self-adhering flowable composite Vertise™ Flow had the lowest and G-aenial Universal Flo® had the highest microtensile bond values.

Bond strength of self-adhesive flowable resin composites to tooth structure

“…Regarding dentin bond strength of SAFRCs, considerable mean variations were also found among included studies, probably due to the same reasons explained for enamel bonding tests. SAFRCs exhibited statistically lower dentin bond strength in contrast to CFRCs (Table 4) 8,9,16,[21][22][23][25][26][27][28][30][31][32][34][35][36][37][38][39] as well as predominant adhesive fail-ures 8,9,22,23,28,30,31,33,[34][35][36][37][38][39] . This indicates a deficient and non-stable chemical interaction between functional monomers incorporated into SAFRCs and dentin microstructure.…”

“…In total, 23 in vitro studies met inclusion criteria (published between 2012 and 2019) 8,9,16,[20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39] and most of them (n=18) used permanent teeth (ranging from 30 to 160) for the bonding tests. The bond strength of SAFRCs to primary teeth was evaluated in six studies, published between 2013 and 2019 16,22,26,30,34,38 . Vertise® Flow (Kerr Corp, Orange, CA, USA) (n=22) followed by Fusio™ Liquid Dentin (Pentron Clinical, Orange, CA, USA) (n=5) were the most tested SAFRCs, while Constic® was evaluated only in three studies 29,35,37 .…”

“…Failure mode analysis was evaluated in 20 of 23 studies, using stereomicroscope/optical microscope, digital microscope and/or Scanning Electron Microscopy (SEM), showing a predominant adhesive failure pattern in SAFRCs groups 8,9,[20][21][22][23][24][27][28][29][30][31][32][33][34][35][36][37][38][39] .…”

The effect of a zirconia primer on the shear bond strength of Y-TZP ceramic to three different core materials by using a self-adhesive resin cement

“…It implies that using this resin cement to bond the zirconia ceramic to composite resin core yielded stronger bond than the cohesive strength of resin composite. [ 36 ] Patil et al reported that the bond strength of the luting cement to composite resin core was higher than that to amalgam core when resin-modified glass ionomer was used as a luting cement. [ 22 ] In the present study, the bond strength of amalgam and composite core was not significantly different, due to the early cohesive failures of composite resin cores within the core material.…”

“…This finding was also reported by other researchers. [ 36 37 38 ] All the failures in the composite resin cores appeared completely cohesive within the composite.…”